Claims made about low carbohydrate diets and what the evidence says

Low carb (Atkins) diets lead to a reduction in appetite

Proponents of this diet point to the research that low carb diets lead to an automatic restriction in calories consumed through a reduction in appetite.

I havn’t seen any opponents of low carb diets actually refute this (though they may be out there). But they make the point that the restriction in carbohydrates makes eating a lot less enjoyable.

This might lead to less calories consumed in the short term, but they point to research demonstrating that it also leads to many people on low carb diets quitting them within 6 months, and then picking up weight again.

Higher levels of initial weight loss

Proponents of Atkins type diets point to research demonstrating that they lead to higher levels of initial weight loss.

My own opinion based on the research out there is that this is probably true. There are a few things that opponents of low carb diets do point to here though:

Firstly, the greater weight loss appears to largely be water. This isn’t necessarily a great thing as key electrolytes are sometimes depleted.

Secondly, the fact low carb diets are difficult to sustain means that this initial greater loss in kilograms over many other diets counts for little after the person falls off the diet. You might want to read the article on what research shows to be the most effective diet for examples of this.

Something I would just like to add to this is that there is a lot of research demonstrating that losing more than a pound (1/2 kg) a week is a bad idea as it tends to lead to a slowing down in one’s metabolism.

Less visceral fat and lower triglycerides on low carb diets?

Proponents of low carb diets believe that they lead to higher proportionate loss of visceral fat (as opposed to subcutaneous fat), especially around the abdominal cavity. In general visceral fat is seen as more dangerous than subcutaneous fat. The theory is that over time this should therefore lead to lower risk of cardiovascular disease and diabetes. They also cite evidence from research that triglyceride levels decrease on this diet.

Many opponents to low carb diets dispute that this is true, or even if it might be up front that it is certainly untrue at the point that weight loss has stabilised. There also appears to be quite a powerful argument (though currently derived from mouse studies) that low carb/high fat diets lead to an increase in hepatic triglycerides. Obviously a fatty liver places you at high risk for several chronic illnesses.

Low carb diets increase HDL as well as the HDL/LDL ratio.

Proponents of low carbohydrate (Atkins type) diets also cite studies that these diets increase high density lipoprotein (HDL) levels. The research studies I have seen demonstrating increased HDL appear pretty conclusive. HDL are the lipoproteins that carry cholesterol from the body to the liver to be processed, and therefore are generally seen as ‘good’. This is because the liver then either reuses them or prepares them to be excreted by the body. This can be compared to low density lipoproteins (LDL) that carry cholesterol from the liver to the body extremities. Both HDL levels and HDL/LDL ratios have been shown to be predictive of lower cardiovascular risk.

Most opponents of low carb diets don’t appear to refute that they tend to increase HDL. Some even agree that the HDL/LDL ratio improves although others are less convinced. However, this is where things get thorny, and where one of the biggest criticisms of low carb/high fat and protein diets comes in to play. Opponents of low carb diets cite several research studies showing (rather emphatically in my opinion) that low carb diets lead to increased LDL levels. Now over the years many different studies have showed strong positive correlations between LDL and cardiovascular risk. Many would argue that this is far more predictive of cardiovascular risk than lower HDL or indeed a high HDL/LDL ratio is (and certainly they would have a lot more evidence to back them up). Recent research appears to demonstrate (not yet conclusively, in my opinion) that after weight loss stabilises on low carb diets cholesterol actually goes up to higher than the original values.

Low carb diets increase the size of LDL

Some proponents of low carb diets claim that LDL does not in fact go up but in my opinion there is little evidence to support this rather hopeful hypothesis against a plethora of studies showing LDL increase.

However, some supporters of low carb diets have come up with the counterpunch on this rather crucial point that although LDL levels may increase, low carb/high fat diets increase the size of the LDL particles! This is apparently a good thing as it is claimed that the smaller the size of the LDL particles the greater the cardiovascular risk.

This theory appears to be an attempt to explain research studies showing a link between smaller LDL particle size and higher risk of cardiovascular disease. The normal theory is that cholesterol builds up on the inside of an artery. However, this theory surmises that it actually begins in the layer of the artery below the epithelium - the artery’s ‘skin’ - when there is damage and inflammation there. LDL particles from the blood then lodge in this sub-epithelial layer and build up from there to form the plaque, and as this grows this plaque begins to block the artery.

So what does all this mean? Well it appears that we need to determine to what extent higher LDL levels are offset by greater LDL particle size (as well as higher HDL levels) in terms of final cardiovascular risk. You might want to refer to my article discussing research on how low carb diets affect cardiovascular risk for more information on this subject.

Proponents of low carb diets also say that they lower blood glucose levels and therefore reduce the insulin spikes. Because high glucose levels are actually toxic to the body we normally respond with a spike in insulin, which communicates that glucose needs to be brought into the cells, where it is then burned or stored. Diabetic people are insulin resistant, meaning that the body does not bring enough blood glucose into the cells. The argument goes that if there isn’t much of a blood glucose spike to begin with then the problem is circumnavigated.

Opponents of the low carb diet do not appear to contest the drop-off in blood glucose levels. I would like to interject with my own point here though, that this result can also be achieved through a low GI (rather than low carb) diet.

What relatively new research has thrown up though is that high protein (and therefore low carb) diets may lead to a significant increase in insulin resistance and therefore actually place people at a higher risk of diabetes. You might want to take a look at my article on .what research says about low carb diets and risk of diabetes.

Low carb diets tend to help lower blood pressure.

Low carb diets are supposed to aid with metabolic problems. The argument appears to go that low carb diets positively impact on the five major symptoms of metabolic syndrome, namely elevated fasting blood sugar levels, abdominal obesity, high triglycerides, low HDL levels and elevated blood pressure. As far as I can discern it does appear that on average people on low carb diets do reduce blood pressure.

It is probably necessary to point out that this isn’t the only dietary way to reduce blood pressure, but it does appear to be one of the more effective ones. I would (again) like to see more research on to what extent low GI diets reduce blood pressure, and whether the reduction in carbohydrates has any unique contribution once the reduction of high GI carbs has been taken into account. The other thing just worth mentioning here is that low carb diets can sometimes deplete the system of electrolytes, which is also a risk factor for HBP.

High carb diets help with epilepsy and autism

It appears that something in the ketogenic (not just low carb/Atkins diet) benefits people with epilepsy, and possibly other brain disorders. There is also evidence that it might help with autism. The mechanism appears to be that parts of the brain might do better when using ketones as an energy source as opposed to just glucose, though the exact pathways appear less certain.

I have read some of the original research on low carb diets and epilepsy and in my opinion it has proved most helpful in this respect. As many as half of epileptics have shown improvement or remission, and many have been able to go off their meds!

Conclusions on low carb diets

Both the actual research and even the propaganda on low carb diets has certainly shaken up the world of nutrition! In my opinion this is awesome. It has made scientists, dietitians and the like take a look outside of their bubble and reassess what they believe. Sadly though, many people have clung to one position or the other, with what in my opinion is a rather adolescent attitude of ‘all good’ or ‘all bad’.

I would encourage you at this juncture to read my articles on what the original research out there appears to say about the effect of low carb diets on cancer, cardiovascular risk and diabetes, and to draw your own conclusions. Too many people appear to read some single and heavily biased article supporting or attacking high carb diets and then cite this as their ‘opinion’ on these diets.

If you are considering starting a low carbohydrate diet then you might as well have an accurate understanding of what you are getting yourself in to.

Briefly though, I have drawn the following tentative conclusions based on the currently available facts and research:

There are clearly some great short-term results from low carb diets, including the reduction in HDL and short-term benefit in terms of diabetes.

The research on ketogenic diets and in particular their effect on the kidneys is quite damning and I would stay away from these. However, in fact very few (<10%) of people on ‘ketogenic’ diets are actually experiencing ketosis and so their ketogenic diets just aren’t ketogenic!

There is also a strong body of evidence that low carb diets can be harmful, and this needs to be taken very seriously.

I would therefore personally not consider an extremist low carb diet at the moment, and particularly as a long-term lifestyle change, as there are still just too many unanswered questions on the subject. However, as mentioned they definitely do have some advantages over standard low-fat diets in the short term, and for specific populations such as epileptics.

Through reading quite a bit about diets I feel most extremist diets have their problems – whether they be extremely low or high in carbohydrate, protein and/or fat. This humble researcher feels that our bodies were designed to be able to digest and process all of these different groups because, oddly enough, we need to consume all of them - but in moderate doses - in order to be healthy!

In line with the above I see a lot of promise in low GI diets with moderate and healthy levels of carbs, fats and proteins. The bottom line is that if people want to lose weight we need to consume less calories! This approach may not have quite the same short-term WOW factor, but is much safer and easier to sustain!

I am a huge fan of sustainable lifestyle change, looking towards long-term health, and in terms of weight loss the only way to guarantee that your weight doesn’t just yoyo is to find that point of equilibrium where food tastes good, is healthy and is not excessive. There are no quick fixes, and ‘short cuts’ tend to take a long-term health consequences!